<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>一列居中</title>
    <link rel="stylesheet" href="one_col.css">
</head>
<body>
<div class="container">
    <div class="header">这是头部</div>
    <div class="content">中间正文</div>
    <div class="footer">联系方式</div>
</div>
</body>
</html>